Appendix H Sfu Geology Letter Report

Trans Mountain Pipeline ULC, TMEP Westridge Tunnel Investigation November 26, 2014 2014 Site Investigation Data Report – FINAL Project No.: 0095-150-15 APPENDIX H SFU GEOLOGY LETTER REPORT 0095150-15 Site Investigation Data Report - FINAL.docx BGC ENGINEERING INC. ENGINEERING GEOLOGY OF BURNABY MOUNTAIN A preliminary report John J. Clague PGeo Doug Stead PEng Allison Westin Mirko Francioni Department of Earth Sciences Simon Fraser University Burnaby, BC V5A 1S6 November 7, 2014 Burnaby Mountain, A Preliminary Report 2 Introduction and summary At the request of BGC Engineering, we provide this interim report focusing on three issues: 1. Did Holocene faulting produced the landforms around Burnaby Mountain? 2. The role that landsliding played in producing the scarp on the north side of Burnaby Mountain 3. An estimate of the retrogression potential of the scarp With regard to the first issue, we have found no evidence of Holocene (active) faulting on Burnaby Mountain. The Eocene rocks that form Burnaby Mountain probably are faulted, but these faults are old structures with no evidence for recent offsets. This interpretation is qualified because we do not have, at this time, borehole logs that have been geotechnically logged. Large slumps produced the steep scarp north of the Simon Fraser University campus and Burnaby Mountain. The slumps are relict, and similar-scale landsliding is very unlikely to happen today. Accordingly, the possibility of significant retrogression of the head scarp is very low, and there is no possibility that retrogression would extend to the west to the proposed tunnel alignment. Geologic setting Burnaby Mountain is developed in Eocene alluvial sandstone, conglomerate, and minor shale. It is a remnant of a larger structurally controlled basin fill that extends from the southern margin of the Coast Mountains on the north to south of Bellingham, Washington, on the south (Mustard and Rouse 1994). The Eocene sedimentary sequence conformably overlies Late Cretaceous marine sediments in Stanley Park. It crops out in building foundations in downtown Vancouver and Capitol Hill, and remnants of Miocene basalt sills and dykes that intrude are exposed at Sentinel Hill in West Vancouver, along the James Cunningham Seawall in Vancouver, in Queen Elizabeth Park in Vancouver, and at Grant Hill east of Maple Ridge (Hamilton and Dostal 1994). During the Early Eocene, the Coast Mountains were uplifted and dissected by erosion. The products of this event were carried into a fault-controlled Burnaby Mountain, A Preliminary Report 3 subsiding basin by rivers flowing from the rising mountains. The Eocene sedimentary rocks were folded, faulted, and uplifted during the Neogene in response to convergence and subduction of the Juan de Fuca plate against North America. What is now Metro Vancouver was covered by the southern margin of the Cordilleran ice sheet at least twice during the Pleistocene (the period from 2.6 million years ago to 11.6 thousand years ago). Southward- and southwestward-flowing ice deeply eroded the Cretaceous and Eocene fill in the Fraser Valley and Strait of Georgia, producing today’s landscape. Glaciers flowing from the Coast Mountains also greatly deepened and broadened Tertiary river valleys into the fiords and fiord lakes that presently indent the Coast Mountains, including Howe Sound, Indian Arm, Coquitlam Lake, and Harrison Lake (Clague 1994). Burrard Inlet may be part of this glacially overdeepened Tertiary river system. Glaciers also deposited thick sequences of non-lithified sediments, including till, glaciofluvial and deltaic sand and gravel, and glaciolacustrine silt. These sediments deeply bury bedrock over much of the Fraser Valley. During late-glacial (ca. 15-12 thousand years ago) and postglacial (12 thousand years ago to present) time, the Fraser River has built its floodplain and delta westward along an arm of the sea in the Fraser Valley into the Strait of Georgia. The delta continues to grow westward into the Strait of Georgia, although its channel is now confined by dykes, localizing deposition to the mouths of the North Arm and Middle and Main channels. Tectonic environment The Neogene tectonic environment in southwestern British Columbia is controlled by (1) subduction of the Juan de Fuca plate beneath the west edge of North America, and (2) clockwise rotation of a sub-block of the North America plate around a Euler pole located in southern Idaho or eastern Washington. The former is responsible for giant earthquakes that occur, on average, once every 500 years (Clague 1997; Goldfinger et al. 2003), and the latter produces crustal compression, folding, and oblique thrust displacements along active faults in Puget Lowland (Fig. 1; Wells et al. 1998). The Coast Mountains act as a buttress to the rotating block to the south. GPS velocities in northwest Washington State and southwest British Columbia suggest broad blocky plate movement, separated by closely Burnaby Mountain, A Preliminary Report 4 spaced, west- to west-northwest-trending active faults (McCaffrey et al. 2007). Using airborne LiDAR imagery, more than ten active faults have been mapped to just south of the International Boundary (Barnett et al. 2010), and one extends across the east end of Juan de Fuca Strait to near and possibly through Victoria. A 4-km fault scarp 35 km northeast of Bellingham in the North Fork Nooksack valley records three large earthquakes in the Holocene (Haugerud et al. 2005; Siedlecki and Schermer 2007). These faults are probably capable of Mw 7 earthquakes. Although no similar faults have been identified in the Fraser Valley, their absence may be more apparent than real because airborne LiDAR images, on which their identification is based, is only now becoming available in this area. Figure 1. Active faults in Puget Lowland (Kelsey et al. (2012). Burnaby Mountain, A Preliminary Report 5 Engineering Geology of Burnaby Mountain The maximum thickness of the Eocene sedimentary sequence on Burnaby Mountain is about 350 m. The Eocene sequence dips uniformly about 6o to the south. This dip gives the mountain its pronounced asymmetry, with a very steep scarp slope on the north and a gentle dip slope on the south (Fig. 2). The lowest exposed Eocene sedimentary rocks (although not the lowest rocks in the Eocene sequence) crop out in a 30-m-high exposure along Barnett Highway on the northwest side of the mountain. This exposure is dominated by conglomerate consisting of rounded to subrounded clasts of dominantly igneous lithologies. The conglomerate has a matrix of sand, granules, and pebbles. The exposure is stable in a near- vertical face, indicating moderate strength. Most of the Eocene sequence above this basal exposure is covered by soil and colluvium; outcrops are few. However, the upper trail system on the steep, north side of Burnaby Mountain and north-draining gullies and ravines high on this slope exposure highly weathered intertonguing sandstone and minor pebbly conglomerate, shale, and coal. These rocks also have sufficient strength to support to steep (locally > 60o) slope on the north side of the mountain. The south slope of the mountain is inclined more gently (average = 6o) than the north slope. We found no outcrops of Eocene rocks at the surface. Rather the rocks are covered by a southward- thickening wedge of late Pleistocene till and glaciomarine sediments. (Armstrong 1990; Armstrong and Hicock, 1980, 1981). Alternating resistant and recessive rock layers are locally evident beneath the sediment cover on the slope slope in airborne LiDAR imagery. Local faults Faults are “fracture(s) or zone(s) of closely associated fractures along which rocks on one side have been displaced with respect to those on the other side” (Bryant and Hart, 2007). Blunden (1971) inferred seven faults crossing Burrard Inlet from North Vancouver to Coal Harbour, two of which he thought showed vertical offsets of about 150 meters. Blunden (1971) concluded that the faults offset late-glacial and early Holocene sediments, and thus are ‘active’ [Note: An ‘active fault’, as the term is commonly used, is one that has slipped in the Holocene, which is the past 11,600 years. More recent work has called into question Blunden’s interpretation, both with regard to the presence of the faults he mapped and the evidence for recent displacements. While mapping in the western Burnaby Mountain, A Preliminary Report 6 Fraser Valley for the Geological Survey of Canada, Johnston (1923) suggested that oil flows along a fault in Burnaby, but no evidence has been found for this structure. Johnston also inferred that a fault extends in an easterly direction beneath Burrard Inlet based on the juxtaposition there of crystalline rocks of the Coast Plutonic Complex to the north and Eocene ` Figure 2. Burnaby Mountain slope map. Note the asymmetry of the mountain, with very steep slopes on the north side and gentle slopes to the south. rocks to the south (Fig. 3). This seems like a reasonable assumption given that the crystalline rocks, which are Late Cretaceous in age, formed at crustal depths of perhaps 10-20 km and the overlying cover rocks was completely stripped off during Tertiary time when the southern Coast Mountains were tectonically elevated. Given the amount of uplift required to elevate the crystalline rocks from deep in the crust to high above sea level, and the small amount of tilting of the Eocene sequence beneath Capitol Hill and Burnaby Mountain, it seems likely that uplift was Burnaby Mountain, A Preliminary Report 7 localized on one or more faults beneath Burrard Inlet. Crampton (1975) identified four major dip-slip normal faults crossing Mount Burnaby based Figure 3. Inferred fault along Burrard Inlet based on adjacent rock units of different age (Johnston 1923). Figure 4. Four purported faults beneath Burnaby Mountain, highlighted in green on the map (Crampton 1975). Burnaby Mountain, A Preliminary Report 8 on stream and gully orientations: two on the west with dips to the west, and two to the east with dips to the east (Fig.

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